Try not to worry, it's normal. After your first baby, they usually don't drop into the pelvis until labor starts. This was the case for me as well--I just had my second little boy, and he didn't drop down until my water broke.
I totally sympathize with you being uncomfortable! The good news is that if your baby does drop before labor starts, your breathing will almost certainly get much easier.
The end is near for you, hang in there!!